循环移位

题目要求：

将字符串str进行循环移位，要求算法空间复杂度O(1),时间复杂度O(n)

思路：

假设str需要循环移位k位，则将其分为前后两部分，分别长k和n-k,称AB

则循环移位的过程即为XY->YX. 可由X^T即转置完成，(X^TY^T)^T=(Y^T)^T(X^T)^T=YX

实现如下：

#include"stdio.h"#include"string.h"void ReverseString(char* str, unsigned int nStart, unsigned int nEnd){char tmp;while(nStart < nEnd){tmp = str[nStart];str[nStart] = str[nEnd];str[nEnd] = tmp;++ nStart;-- nEnd;}}void RightReverse(char* str, unsigned int nBit, unsigned int nLen){//avoid exceptionif (nBit > 0 && nLen > 0){ReverseString(str, 0, nLen - 1);ReverseString(str, 0, nBit - 1);ReverseString(str, nBit, nLen - 1);}}void LeftReverse(char* str, unsigned int nBit, unsigned int nLen){//avoid exceptionif (nBit > 0 && nLen > 0){ReverseString(str, 0, nBit - 1);ReverseString(str, nBit, nLen - 1);ReverseString(str, 0, nLen - 1);}}int main(){const int MAXLEN = 64;char str[MAXLEN] = {0};unsigned int kBit, len;printf("Please input the string and start from the bit:");while (scanf("%s%d", str, &kBit) != EOF){len = strlen(str);if (kBit > len)kBit %= len;RightReverse(str, kBit, len);LeftReverse(str, kBit, len);printf("%s\n",str);}}